CAMP SIGNALING MECHANISMS WITH AGING IN THE CERATITIS-CAPITATA BRAIN

Aging has been associated with alterations in protein phosphorylation, This study was undertaken to examine eventual changes in cAMP-depende nt protein kinase (PKA) activity and enzyme regulatory subunit levels from the dipterous Ceratitis capitata brain with postmaturational agin g and senescence. PKA activity was determined in cytosolic and membran e fractions of the C. capitata brain during the adult stage of the ins ect lifespan. PKA activity markedly increased at the first stages of t he life of the fly both in cytosol and in membranes. A lower peak of P KA activity was evident both in particulate and cytosolic fractions in the terminal phase of the life of the fly. Thus, PKA activity was sig nificantly higher in the brain of mature flies when compared to the br ain of aged flies. It is possible that increases in cAMP-dependent pro tein phosphorylation levels characterize the terminal aging process in the insect nervous tissue. On the other hand, levels of regulatory (R ) subunit were also measured in membranes and cytosol by immunoblottin g. Cytosolic regulatory subunit levels were more elevated near the ter minal phase of life, whereas in membranes, regulatory subunit levels d ecrease in senescence in parallel with particulate PKA activity. The i ncreased R subunit level in citosol may reflect a cellular response me chanisms to down-regulate the kinase system in aged flies. (C) 1997 El sevier Science Ireland Ltd.